1. Field of the Invention
The present invention relates to a method for producing a cyclohexanone oxime from a cyclohexanone using ammonia and hydrogen peroxide. The cyclohexanone oxime is useful as a starting material for producing an xcex5-caprolactam, or the like.
2. Description of the Related Art
For producing a cyclohexanone oxime, there has been proposed a method of reacting cyclohexanone with hydrogen peroxide and ammonia in the presence of titanium silicate catalyst (e.g., Japanese Patent Application Laid-Open No. (JP-A-)62-59256 corresponding to U.S. Pat. No. 4,745,221; JP-A-6-49015 corresponding to U.S. Pat. No. 5,312,987; JP-A-6-92922 corresponding to U.S. Pat. No. 5,227,525; and JP-A-7-100387 corresponding to U.S. Pat. Nos. 5,683,952, 5,691,266 and 5,874,596). Such a method has advantages in that it does not need to neutralize sulfuric acid with ammonia, while the neutralization is conducted in the conventional method for producing cyclohexanone oxime with hydroxylamine sulfate, and in that product separation from the catalyst can be readily carried out since a solid catalyst is utilized.
However, in the above-reaction of cyclohexanone with hydrogen peroxide and ammonia, a catalytic activity of the titanium silicate catalyst is gradually deteriorated with a passage of reaction time so that the conversion rate of cyclohexanone may be insufficient.
One of objects of the present invention is to provide a method in which inactivation of the titanium silicate is suppressed in a reaction of cyclohexanone with hydrogen peroxide and ammonia, thereby producing a cyclohexanone oxime in high yield.
As a result of eager study by the present inventors, it has been found that the above object and other objects can be achieved by performing the reaction of cyclohexanone in the presence of a titanium silicate together with a silicon compound other than the titanium silicate, and the present invention has been accomplished.
The present invention provides a method for producing a cyclohexanone oxime, the method comprising the step of reacting a cyclohexanone with hydrogen peroxide and ammonia in the presence of a titanium silicate and a silicon compound other than the titanium silicate.
In the present invention, a cyclohexanone oxime is produced by an ammoximation of cyclohexanone, in which a cyclohexanone is reacted with hydrogen peroxide and ammonia in the presence of a titanium silicate and a silicon compound other than the titanium silicate.
A titanium silicate to be used in the present invention may be a zeolite comprising titanium, silicon and oxygen as elements in its skeletal structure. The titanium silicate may have a skeletal structure substantially constituted of titanium, silicon and oxygen, or of an optional other elements in addition to these elements. The titanium silicate may have an atomic ratio of silicon to titanium of from 10 to 1000, and may have the shape of fine powder, pellet or the like. The titanium silicate can be prepared by a method disclosed in JP-A-56-96720 corresponding to U.S. Pat. No. 4,410,501 or the like.
In the present invention, by using such a titanium silicate and a silicon compound other than the titanium silicate, a cyclohexanone is reacted with hydrogen peroxide and ammonia to obtain a cyclohexanone oxime.
A cyclohexanone to be used as a starting material in the prevent invention may be obtained, for example, by oxidation of a cyclohexane, by hydration of a cyclohexene, followed by dehydrogenation, or by hydrogenation of a phenol.
The hydrogen peroxide to be used in the prevent invention may be produced by the so-called anthraquinone method. The anthraquinone method can be conducted, for example, by a process in which an xcex1-ethylanthraquinone is dissolved in a water-insoluble solvent such as a benzene, which is then subjected to catalytic hydrogenation reaction to obtain a hydroanthraquinone, and the hydroanthraquinone is oxidized to an xcex1-ethylanthraquinone while providing hydrogen peroxide. Commercially available hydrogen peroxide, which is an aqueous solution having a concentration of about 10% by weight to about 70% by weight, may also be used in the present invention. The relative molar amount of the hydrogen peroxide is preferably in the range of from about 0.5 mol to about 3 mol, and is more preferably in the range of from about 0.5 mol to about 1.5 mol, based on 1 mol the cyclohexanone. The hydrogen peroxide used in the present invention may contain a stabilizer including, for example, a phosphate salt such as a sodium phosphate, a polyphosphate salt such as a sodium pyrophosphate and a sodium tripolyphosphate, a pyrophosphoric acid, an ascorbic acid, an ethylenediamine-tetraacetic acid, a nitro tri-acetic acid, an amino tri-acetic acid, a diethylenetriamino penta-acetic acid, and the like.
In the present invention, ammonia may be used in a gaseous form, in a liquid form, or in a solution form using water, an organic solvent or the like. The relative molar amount of the ammonia is preferably about 1 mol or more, and is more preferably about 1.5 mol or more, based on 1 mol of the cyclohexanone.
The reaction for producing a cyclohexanone oxime with ammonia and hydrogen peroxide may be performed in a solution using a solvent. Examples of the solvent include an alcohol such as a methyl alcohol, an ethyl alcohol, a n-propyl alcohol, an isopropyl alcohol, a n-butyl alcohol, a sec.-butyl alcohol, a tert.-butyl alcohol and a tert.-amyl alcohol; water; and a mixture thereof.
In the present invention, the reaction for producing a cyclohexanone oxime using ammonia and hydrogen peroxide is performed in the presence of a titanium silicate together with a silicon compound other than the titanium silicate. (Hereinafter, the silicon compound other than the titanium silicate may be simply referred to as xe2x80x9csilicon compoundxe2x80x9d in some cases). By using the silicon compound with the titanium silicate, inactivation of the titanium silicate can be suppressed, and therefore, the amount of the titanium silicate to be used as the catalyst in the reaction can be reduced. In view of cost reduction, it is preferred to use a less expensive silicon compound than a titanium silicate, which is usually relatively expensive. The silicon compound, in itself, may substantially have no catalytic activity in the reaction.
Examples of the silicon compound include a compound containing silicon and oxygen, such as a silica gel, a silicic acid and a silicate. Also, a crystalline silica gel and a metallo-silicate, each of which has a zeolite-like structure, are preferably used. The silicon compound may be used singly, or two or more of the silicon compounds may be used in combination, if necessary.
In the present invention, the titanium silicate and silicon compound are preferably used in a concentration, respectively, of from about 0.1% by weight to about 10% by weight based on the liquid portion of the reaction mixture, so that the titanium silicate and silicon compound are suspended in the mixture.
The effect of suppressing the inactivation of catalytic activity of the titanium silicate is remarkable especially when water is present in the reaction mixture at a concentration of about 10% by weight or more.
The reaction for producing a cyclohexanone oxime using ammonia and hydrogen peroxide may be conducted batch-wise, or may be conducted in a continuous manner. The batch-wise reaction may be carried out, for example, by a method in which a reactor is charged with a cyclohexanone, ammonia, a titanium silicate, a silicon compound and a solvent, into which hydrogen peroxide is introduced, while stirring; or by a method in which a reactor is charged with a cyclohexanone, a titanium silicate, a silicon compound and a solvent, into which hydrogen peroxide and ammonia are introduced, whole stirring; or by a method in which a reactor is charged with a titanium silicate, a silicon compound and a solvent, into which a cyclohexanone, hydrogen peroxide and ammonia are introduced, while stirring. The continuous reaction may be carried out, for example, by a method in which a suspension of a titanium silicate and a silicon compound is prepared in a reactor, into while a cyclohexanone, hydrogen peroxide, ammonia and a solvent are further introduced, while a liquid portion of the resulting reaction mixture is extracted through a filter from the reactor. It is preferred to use a glass-lining reactor, a stainless steel reactor or the like in view of avoiding decomposition of the hydrogen peroxide.
The reaction temperature may be in the range of from about 50xc2x0 C. to 100xc2x0 C. The reaction may be performed at a normal pressure, and is preferably under pressure in order to increase the solubility of ammonia into a liquid portion of the reaction mixture. In the case of the reaction under pressure, the pressure may be adjusted by using an inert gas such as nitrogen gas and helium gas.
The post handling procedures, such as separation of the cyclohexanone oxime from the reaction mixture, is not limited and may be carried out appropriately using a known methods. For example, the separation of the cyclohexanone oxime may be conducted in a manner such that the titanium silicate and silicon compound is separated from the reaction mixture by filtration or the like to obtain a liquid portion of the reaction mixture, followed by distillation of the liquid portion.
In accordance with the present invention, a cyclohexanone is reacted with hydrogen peroxide and ammonia with suppressing the inactivation of a titanium silicate as a catalyst, to produce a cyclohexanone oxime in high yield.
The invention being thus described, it will be apparent that the same may be varied in many ways. Such variations are to be regarded as within the spirit and scope of the invention, and all such modifications as would be apparent to one skilled in the art are intended to be within the scope of the following claims.
The entire disclosure of the Japanese Patent Application No. 2002-189450 filed on Jun. 28, 2002, indicating specification, claims and summary, are incorporated herein by reference in their entirety.